Method of making synthetic brush bristles



Aug. 29, 1950 E. H. HAUX 2,520,502

METHOD OF MAKING SYNTHETIC BRUSH BRISTLES Filed June 30, 1948 2 Sheetls-Sheet 1 i 38 Funny wglu li, 42 4 may IN VEN TOR. f2 ME /EH hm/x HTTOE/VEK Aug. 29, 1950 E. H. HAUX METHOD OF MAKING SYNTHETIC BRUSH BRISTLES 2 Sheets-Sheet 2 Filed June 30, 1948 HTTOR/VEK Patented Aug. 29, 1950 METHOD OF MAKING SYNTHETIC BRUSH. BEISTLES Elmer H. iiaux, Pittsburgh, Pa., assignor to Pittsburgh Plate Glass Company, Pittsburgh, Pa, a corporation of Pennsylvania Application June 30, 1948, Serial No. 36,243

5 Claims. (01. 1854) The present invention relates to the method of making synthetic bristles as substitutes for animal bristles in brushes such as paint brushes or the like, and it has particular relation to synthetic bristles comprising cellulose esters.

One object of the invention is to provide a method of making bristles which, when assembled in a brush, have a high capacity for retaining paint without running or spattering during brushing operations.

A second object, is to provide a method of making bristles which, when assembled in a brush, have uniform resiliency in all directions of brushing.

A third object is to obviate cohesion of a multiplicity of bristles, when passing from a spinner head into a setting bath.

These and other objects of the invention, will be apparent from consideration of the following specification and claims.

For a better understanding of the invention, reference may be had to the drawings, in which;

Fig. 1 is a sectional view of a brush constructed in accordance with the provisions of the invention.

Fig. 2 is a diagrammatic or schematic view of an apparatus, suitable for use in the spinning of bristles, in accordance with the provisions of the invention.

Figs. 3 and 4 are sectional views showing, on an enlarged scale, various forms which the bristles embodying the invention, may take.

Fig. 5 is a fragmentary portion of a filament embodying a plurality of bristle sections before cutting to length.

Fig. 6 is an elevational view of a bristle cut from a filament.

Fig. 7 is a detailed view of a plate having a plurality of spinnerette openings formed therein,

and adapted to be employed in practicing the in- 1 vention.

In the drawings, like numerals refer to like parts, throughout.

As is well known, brushes such as are employed in the spreading of paint and other coating compositions, conventionally are formed of animal bristles or hairs appropriately grouped together into brush or bristle portions, and suitably attached to a handle. Animal bristles, at least of the better types, are relatively circular in section and are also tapered from butt portion to tip. The tips may also be substantially frayed or flagged, and the surfaces usually are covered with, or formed of, overlapping plates or scales, thus providing surfaces whichretain paint or other a n material when the brush is dipped therein, with a minimum tendency of thepaint to spatter, or to run back down the handle when the brush, is tipped upwardly. Since the bristles are substantially round in section, they also have approximately similar brushing characteristics in all directions.

As a result of worldwide war conditions, bristles of a high grade are now very difiicult, if not in possible, to obtain and even under normal condi+ tions, the supply and prices thereof are subject to wide fluctuations. Accordingly, it has been mm posed to form bristles suitable for paint brushes or similar brushes, by spinning filaments: of plastic materials such as cellulose triacetateor nys lon, into long filaments or strands which can be cut up into lengths appropriate for assembly into brushes. Much diificulty has been experienced in obtaining synthetic bristles which simulate the natural products in all of their properties. Particular difficulty is experienced in obtaining a bristle which will retain an adequate quantity of paint or other coating material when a brush em bodying the bristles is dipped therein, and which, after the brush has been charged, is not subject to an excessive tendency to spatter or run. In order to improve the paintwetaining characteristics of the bristles, it has been proposed to roughen the surfaces, especially the tip portions, by contacting the bristles either before or after assembly into brushes, with a common abrasive wheel or other bufling agency. Such operation obviously requires considerable labor and is comparatively expensive. Also it is relatively dimcult, by such operation, to obtain adequate contact of the buffing agency with the bristles disposed in the center of the bunch.

In accordance with the present invention, it is proposed to form bristles for paint brushes embodying narrow, deep, longitudinally extending grooves or channels of ceratoid cusp cross section, and having side walls close together and in cross section, approximating at least in certain portions, parallelism so that a high degree of capillary attraction for paints and the like is obtained. These bristles are best formed by a, spinning operation involving the inclusion of a solution of cellulose diacetate or cellulose acetate-butyrate, through suitable spinners into a coagulating bath,

' such as mineral spirits adapted to act as a solvent for the solvent content in the filaments.

Example I Cellulose eceto-butyrate is particularly well adapted for use in formin bristles in accordance with the provisions of the invention. Cellulose aceto-butyrate, for example, comprising 18 to 22% butyrate radical, and 38 to 42% acetate radical, is dissolved in a solvent of cellulose acetate butyrate, e. g. in methylene chloride. The ratio of the ester to the solvent may vary over a substantial range, dependent upon the viscosity desired in the spinning solution. However, satisfactory results have been obtained by employing a solution comprising 1800 parts by weight, of cellulose aceto-butyrate and 5800 to 9006, e. g. 7020 parts by weight, of methylene chloride. The spinning characteristics of the solution are substantially improved by including in the coinposition, some liquid hydrocarbon soluble in the methylene chloride, such as mineral spirits, e. g.

400 parts by weight, in the solution above described. The mineral spirits, it is found, substantially reduce the tendency of the filaments to cohere or cling together when they are spun in multiple, through a spinner head having many spinnerette openings formed therein. The mineral spirits incorporated into the solution of cellulose aceto-butyrate, may vary over a considerable range, from the ratio of 400 parts by weight,. above described. The mineral spirits may, for example, be within a range of 300 to 800 parts by weight, in the solution above described. If the ratio of spirits is too low, the filaments will tend to adhere at points of contact. If the ratio is excessively increased, however, premature setting of the plastic ultimately will occur. These effects must be guarded against.

The filaments are spun into a bath of mineral spirits or other liquid non-solvent, such as kerosene, xylene, or the like, designed to set acetobutyrate by extraction of solvent therefrom. Subsequently, the filaments are passed through a dryer, where the last traces of solvent and setting medium are evaporated. The bristle sections are then cut to length.

It is to be understood that the filaments are formed with recurrent constrictions in diameter, corresponding to the taper of the bristle units which are to be formed from the filament. This is best effected by application of a pulsating pressure to the solution of plastic, in order to force it through the spinning head in spurts.

Apparatus for spinning filaments suitable for cutting into bristles 8, is shown diagrammatically in Fig. 2, and embodies a pulsating pump apparatus 9, for delivering a solution of cellulosic ester under pressure. The pump may be of the form. shown and described in patent app ications of John J. Gregory, Serial No. 459,251, now Patent No. 2,374,744, May 1, 1945, and Serial No. 459,252, filed September 22, 1942, now abandoned. Since this pump is not a part of the present invention, it is not described in detail. The pump is connected by conduit in, to a source of solution of plastic, and is connected by means of a suitable conduit H, with the spinning head i2, disposed ina trough l3, containing the mineral spirits constituting the liquid setting agency. The spinning head i2, is provided with a plate l4, having a multiplicity of small spinnerette openings l6, formed therein. Preferably, these openings are circular in section and usually, there will be a large number of them, varying within the range of about 200 to 400, but in Fig. 7, the plate I4 is illustrated as containing only a few of these openings, since it is impossible to show them in any great number, because of their smallness and the small scale of the drawings.

The filaments, after setting in the bath, are

collected into a bunch or cable, and passed about a suitable pulley l6c, and then upwardly about a series of take-up rollers H, which may be driven at a constant speed, in order to maintain suflicient tautness in the reach of filament, in the setting bath. From the take-up rollers, the filaments pass to drying chamber l8, which may be of substantially any convenient design, and wherein heat is supplied to drive off non-solvents and setting agent clinging to, or absorbed in, the body of the filament. After drying, the filaments are passed about pulleys or drums l9 and 23, of a mechanism designed to cut them into sections through their thickest portions, in such manner that each section includes two lengths of bristles. A suitable mechanism for performing the cutting operation, is disclosed in the John J. Gregory application for U. S. Patent, Serial No. 499,264, filed August 19, 1943, now issued as Patent 2,355,841, August 29, 1944. The bristles, in bunches of appropriate size, are then fastened together in any convenient manner, for transmission to the brush makers.

The nature and form of the bristles and the filaments, will be more readily apparent by con sideration of Figs. 3, 4 and 5 of the drawings. In Fig. 5, is shown a portion of one of the filaments, embodying a plurality of brush bristle lengths all joined together in a continuous strand, as they are received from the spinning and drying apparatus. It will be observed that the filament comprises alternating thick; portions 22, and restricted portions 23, c sponding respectively to the butts and the tics of the bristles which are cut from the fil These alternating thickened and constricted por tions are produced by. the pulsation of the pressure generated by the pump 9. In Figs. 5 and no particular attempt has been made to represent the bristles in their actual thickness, sinc they obviously are too small in diameter for accurate representation in that manner. Probably they will be of an average denier of 20 to 4500. ratio of thickness of the constricted portion to thickened portion, will be about 1 to 1.75, but may vary considerably.

Sections of the bristles upon a magnified scale are shown in Figs. 3 and 4; that of Fig. 3 corresponding to the sections obtained by the spinning of cellulose aceto-butyrate, and that of Fig. 4 corresponding to filaments obtained by spinning of cellulose diacetate, i. e. cellulose ester of acetic acid, which is about 59 percent acetylated. It is to be observed that each bristle is formed with one or more deep narrow grooves, such as the grooves 26, 21, 28 and 29, shown in Fig. 3, or 3|, 32, 33 and 34 shown in Fig. 4. These grooves, in section, roughly approximate a conventional pen-point or ceratoid cusp, in outline, and it will be noted that in each instance, the side walls thereof, approach parallelism so that deep channels are formed, designed to have a high degree of capillarity. Such capillarity is found greatly to assist in taking up paints, varnishes and the like liquids, which it may be desired to apply to a surface by means of brushes embodying the bristles. The channels, it may be stated, extend substantially from butt to tip of each bristle regardless of the tapering. It is further to be observed that the bristle sections, although they are highly irregular in outline, nonetheless are of such nature that the bristles, when bent, will flex nearly equally well in any lateral direction. This is an advantage over some bristle forms in which the bristles tend to bend more readily in one direction than the other.

The assembly of the improved bristles into a brush, such as that illustrated in Fig. 1 of the drawings, may follow substantially any convenient procedure. The bristles may be collected together in bunches of assorted sizes, in order to give any desired brush characteristics to the ultimate product. It is also apparent that the synthetic bristles, as thus obtained, may be admixed with any desired ratio of natural bristles, such as pig bristles, ox hair, horse hair or the like, which may be employed in the manufacture of bristles.

A convenient mode of preparing a brush, such as that represented in Fig. 1 of the drawings, involves bunching the bristles together to form a brush portion 30, of suitable size and outline, then inserting the butt portions of the bristles with spacer strips or bars 31 in place, in a conventional sheet metal ferrule 38. The assembly of bristles and spacer strips in the ferrule, preferably, are impregnated in rubber or other adhesive material in order to effect a bond. The cementing material can be cured by heat, or other means, in order to obtain thorough hardening, with resulting complete bondings of the bristles and spacer elements. The butt portion 39 of the handle 4|, is inserted in the upper end of the ferrule and, for purposes of security, nails 32 are driven through the ferrule end of the butt portion of the handle. Similar nails may also be driven into the butt portions of the bristles of the brush 36, in order to provide greater security of the bristles in the handle.

The forms of the invention herein shown and described are to be regarded merely as exemplary, and it will be apparent to those skilled in the art, that numerous modifications may be made therein, without departure from the spirit of the invention or the scope of the appended claims.

This application is a continuation in part of my copending application Serial No. 538,278, filed June 1, 1944, now abandoned.

What I claim is:

1. A method of forming bristles suitable for fabrication into brushes for painting operations, and being tapered from butt to tip, each bristle having longitudinal grooves formed therein, the grooves being of approximate pen-point shape in section, so that the sides approach parallelism to obtain a high degree of capillarity, which method comprises spinning a solution of 1800 parts by weight of a cellulose ester of a group consisting of cellulose diacetate and cellulose aceto-butyrate in 5000 to 9000 parts by weight of methylene chloride as a plurality of individual filaments, into a liquid petroleum hydrocarbon adapted to extract the solvent and set the resultant filaments, the spinning operation being accompanied by pulsations of pressure in order to produce tapering of the bristles, corresponding in length to the desired bristles.

2. A method as defined in claim 1, in which the petroleum hydrocarbon in an amount sufficient to eliminate adhesion of the filaments to each other in the spinning operation, and insuificient to cause premature coagulation of the solution of cellulose ester, is incorporated into the said solution prior to the spinning operation.

3. In a method of forming bristles suitable for fabrication into brushes for painting operations, and being tapered from butt to tip, each bristle having longitudinal grooves formed therein, the grooves being of approximate ceratoid cusp section so that the sides approach parallelism to obtain a high degree of capillarity, the steps which comprise spinning out as continuous filaments a solution of 1800 parts by Weight of cellulose acetobutyrate and 5000 to 9000 parts by weight of methylene chloride into a liquid bath of petroleum hydrocarbon adapted to extract the methylene chloride and set the resultant filaments, the spinning operation being accompanied by pulsations of pressure in order to produce tapering of the bristles in sections corresponding to the length of the desired bristles.

4. In a method of forming bristles suitable for fabrication into brushes for painting operations and being tapered from butt to tip, each bristle having longitudinal grooves formed therein, the grooves being of approximate ceratoid cusp section so that the sides approach parallelism to obtain a high degree of capillarity, the steps which comprise spinning simultaneously a plurality of filaments of a solution of 1800 parts by weight of cellulose acetobutyrate dissolved in 5000 to 9000 parts by weight of methylene chloride containing 300 to 800 parts by weight of mineral spirits preventing cohesion of the filaments, into a bath of a liquid petroleum hydrocarbon adapted to extract the methylene chloride and set the resultant filaments, the spinning operation being accompanied by pulsations of pressure in order to produce tapering of the bristles in lengths cor responding to the desired bristles.

5. In a method of forming bristles suitable for fabrication into brushes for painting operations and being tapered from butt to tip, each bristle having longitudinal grooves formed therein, the grooves being of approximate ceratoid cusp transverse section so that the sides approach parallelism to obtain a high degree of capillarity, the steps which comprise spinning simultaneously into a hydrocarbon bath a plurality of filaments of a solution of a cellulose ester of a group consisting of cellulose diacetate and cellulose acetobutyrate in a suitable solvent containing a petroleum hydrocarbon in an amount suificient to eliminate adhesion of the filaments to each other in the spinning operation and insufficient to cause premature coagulation of the solution of cellulose ester, the spinning operation being accompanied by pulsations of pressure in order to produce tapering of the bristles in sections corresponding in length to the desired bristles.

ELMER H. HAUX.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,036,861 Dreyfus et a1 Apr. 7, 1936 2,143,205 Muller et al. Jan. 10, 1939 2,374,744 Gregory May 1, 1945 

3. IN A METHOD OF FORMING BRISTELS SUITABLE FOR FABRICATION INTO BRUSHES FOR PAINTING OPERATIONS, AND BEING TAPERED FROM BUTT TO TIP, EACH BRISTLE HAVING LONGITUDINAL GROOVES FORMED THEREIN, THE GROOVES BEING OF APPROXIMATE CERATOID CUSP SECTION SO THAT THE SIDES APPROACH PARALLEIMS TO OBTAIN A HIGH DEGREE OF CAPILLARITY, THE STEPS WHICH COMPRISE SPINNING AOUT AS CONTINUOUS FILAMENTS A SOLUTION OF 1800 PARTS BY WEIGHT OF CELLULOSE ACETOBUTYLENE AND 5000 TO 9000 PARTS BY WEIGHT OF METHYLENE CHLORIDE INTO A LIQUID BATH OF PETROLEUM HYDROCARBON ADAPTED TO EXTRACT THE METHYLENE CHLORIDE AND SET THE RESULTANT FILAMENTS, THE SPINNING OPERATION BEING ACCOMPANIED BY PULSATIONS OF PRESSURE IN ORDER TO PRODUCE TAPERING OF THE BRISTLES IN SECTIONS CORRESPONDING TO THE LENGTH OF THE DESIRED BRISTLES. 